Merge branch 'master' into next

Signed-off-by: David Ahern <dsahern@gmail.com>

include/namespace.h

@@ -49,6 +49,8 @@ static inline int setns(int fd, int nstype)
 }
 #endif /* HAVE_SETNS */
 
+void netns_save(void);
+void netns_restore(void);
 int netns_switch(char *netns);
 int netns_get_fd(const char *netns);
 int netns_foreach(int (*func)(char *nsname, void *arg), void *arg);

ip/ip.c

@@ -159,6 +159,7 @@ static int batch(const char *name)
 			if (!force)
 				break;
 		}
+		netns_restore();
 	}
 	if (line)
 		free(line);

ip/ip6tunnel.c

@@ -299,6 +299,8 @@ static int parse_args(int argc, char **argv, int cmd, struct ip6_tnl_parm2 *p)
 		p->link = ll_name_to_index(medium);
 		if (!p->link)
 			return nodev(medium);
+		else
+			strlcpy(p->name, medium, sizeof(p->name));
 	}
 	return 0;
 }

ip/ipnetns.c

@@ -708,6 +708,7 @@ static int netns_add(int argc, char **argv, bool create)
 	close(fd);
 
 	if (create) {
+		netns_save();
 		if (unshare(CLONE_NEWNET) < 0) {
 			fprintf(stderr, "Failed to create a new network namespace \"%s\": %s\n",
 				name, strerror(errno));

lib/namespace.c

@@ -15,6 +15,35 @@
 #include "utils.h"
 #include "namespace.h"
 
+static int saved_netns = -1;
+
+/* Obtain a FD for the current namespace, so we can reenter it later */
+void netns_save(void)
+{
+	if (saved_netns != -1)
+		return;
+
+	saved_netns = open("/proc/self/ns/net", O_RDONLY | O_CLOEXEC);
+	if (saved_netns == -1) {
+		perror("Cannot open init namespace");
+		exit(1);
+	}
+}
+
+void netns_restore(void)
+{
+	if (saved_netns == -1)
+		return;
+
+	if (setns(saved_netns, CLONE_NEWNET)) {
+		perror("setns");
+		exit(1);
+	}
+
+	close(saved_netns);
+	saved_netns = -1;
+}
+
 static void bind_etc(const char *name)
 {
 	char etc_netns_path[sizeof(NETNS_ETC_DIR) + NAME_MAX];
@@ -61,6 +90,8 @@ int netns_switch(char *name)
 		return -1;
 	}
 
+	netns_save();
+
 	if (setns(netns, CLONE_NEWNET) < 0) {
 		fprintf(stderr, "setting the network namespace \"%s\" failed: %s\n",
 			name, strerror(errno));